1. Field of the Invention
The present invention relates to a technique to wind fiber bundles around a mandrel.
2. Description of Related Art
There has been known a so-called large-supply helical winding device that supplies fiber bundles to a mandrel from a plurality of guide portions (for example, Japanese Patent Application Publication No. 2009-119803 (JP 2009-119803 A)). The helical winding device described in JP 2009-119803 A includes: a group of guide tubes placed at even intervals along a circumferential direction of a guide ring; and a phase switching structure that changes a circumferential position of the group of guide tubes between a first position (a position in a first state) and a second position (a position in a second state).
When the fiber bundles are supplied to the mandrel from the guide tubes, the fiber bundles are wound around the mandrel by helical winding. The wound fiber bundles thus form a reinforcing layer around the mandrel, and hereby, a tank such as a pressure container is manufactured.
In the technique described in JP 2009-119803 A, at the time when the fiber bundles are wound around the mandrel by the helical winding, a gap might be caused between the fiber bundles wound around the mandrel in an in-plane direction of the reinforcing member. Particularly, a gap might be caused between the fiber bundles in that straight portion of the mandrel which has a constant diameter. Herein, the “gap between the fiber bundles” indicates a gap in the in-plane direction (a direction along a surface of the mandrel) of the reinforcing member formed by winding the fiber bundles.
When the gap is caused between the fiber bundles thus wound around the mandrel, such a possibility occurs that strength of a manufactured tank cannot be improved sufficiently. Further, in a case of using fiber bundles having a broadened width to reduce the occurrence of the gap between the fiber bundles, large guide tubes are required to supply the fiber bundles. Therefore, in order to prevent interference between adjacent guide tubes, an interval between the adjacent guide tubes may be enlarged, which limits placement positions of the guide tubes. In a case where fiber bundles having a width broadened by use of the guide tubes of which the placement positions are limited are wound around the mandrel, a gap may be caused between the fiber bundles having a broadened width.
In view of this, a technique to reduce occurrence of a gap between fiber bundles wound around a mandrel is expected. Further, a technique to reduce in-plane overlap between fiber bundles to be wound around the mandrel is expected. Further, in the techniques, it is desired to simplify a manufacturing process and to reduce a manufacturing cost.